Analysis of the Choroid and Its Relationship with the Outer Retina in Patients with Diabetes Mellitus Using Binarization Techniques Based on Spectral-Domain Optical Coherence Tomography

Reduced macular thickness and vascular density in abnormal glucose metabolism patients: A meta-analysis of optical coherence tomography (OCT) and OCT angiography studies

BACKGROUND

Alterations in macular thickness and vascular density before clinically visible diabetic retinopathy (DR) remain inconclusive. This study aimed to determine whether retinal manifestations in abnormal glucose metabolism (AGM) patients differ from those in the healthy individuals.

METHODS

PubMed, Embase, and Web of Science were searched between 2000 and 2021. The eligibility criteria were AGM patients without DR. Primary and secondary outcomes measured by optical coherence tomography (OCT) and OCT angiography (OCTA) were analyzed and expressed as standardized mean differences (SMDs) with 95% confidence intervals (CIs). A random-effects model was used in the data synthesis. The potential publication bias for the variables was evaluated using Egger's test.

RESULTS

A total of 86 observational studies involving 13,773 participants and 15,416 eyes were included. OCT revealed that compared to healthy controls, the total macular thickness of AGM patients was thinner, including the thickness of fovea (-0.24, 95% CI [-0.39, -0.08]; P  = 0.002, I2  = 87.7%), all regions of parafovea (-0.32, 95% CI [-0.54, -0.11]; P  = 0.003; I2  = 71.7%) and the four quadrants of perifovea; the thickness of peripapillary retinal nerve fiber layer (pRNFL), macular retinal nerve fiber layer (mRNFL), and ganglion cell layer (GCL) also decreased. OCTA indicated that the superficial and deep vascular density decreased, the foveal avascular zone (FAZ) area enlarged, and the acircularity index (AI) reduced in AGM individuals.

CONCLUSIONS

Retinal thinning and microvascular lesions have occurred before the advent of clinically detectable DR; OCT and OCTA may have the potential to detect these preclinical changes.

REGISTRATION

PROSPERO; http://www.crd.york.ac.uk/prospero/ ; No. CRD42021269885.

Macular choroidal thickness, volume, and vascularity index in patients with systemic sclerosis

PURPOSE

The aim of this study was to investigate choroidal parameters in patients with systemic sclerosis (SSc) using enhanced depth imaging spectral-domain optical coherence tomography (EDI-SD-OCT) and to determine their relationships with clinical variables and ocular features.

METHODS

Thirty-three patients with SSc and 40 controls were enrolled. The groups did not differ with regard to age, sex, and axial length. The mean choroidal thickness and volume were obtained in each conventional Early Treatment of Diabetic Retinopathy Study grid subfield. The choroidal vascularity index (CVI), which provides a quantitative analysis of vasculature by calculating the proportion of the luminal area (LA) to the total choroidal area (TCA), was determined.

RESULTS

Lower choroidal thickness and volume were observed in the SSc group. The CVI was significantly higher in SSc patients, whereas the TCA, LA, and stromal area were significantly lower in the SSc group; however, the significant difference of the stromal component was more pronounced than that of the luminal component. Regression analyses did not identify any clinical factors associated with the CVI (except Ca-blocker use), central macular thickness, or volume. No significant differences in choroidal parameters were found within the SSc subtypes (diffuse cutaneous systemic sclerosis (dcSSc) vs. limited cutaneous systemic sclerosis (lcSSc)), or between eyes stratified according to SSc pattern (early, active, or late) using nailfold capillaroscopy (p > 0.05 for all).

CONCLUSION

Our results, with notably higher CVI values, may shed new light on choroidal impairment in patients with SSc. Stromal involvement appeared to dominate the vascular component.

Three-dimensional choroidal vascularity index and choroidal thickness in fellow eyes of acute and chronic primary angle-closure using swept-source optical coherence tomography

AIM

To compare the three-dimensional choroidal vascularity index (CVI) and choroidal thickness between fellow eyes of acute primary angle-closure (F-APAC) and chronic primary angle-closure glaucoma (F-CPACG) and the eyes of normal controls.

METHODS

This study included 37 patients with unilateral APAC, 37 with asymmetric CPACG without prior treatment, and 36 healthy participants. Using swept-source optical coherence tomography (SS-OCT), the macular and peripapillary choroidal thickness and three-dimensional CVI were measured and compared globally and sectorally. Pearson's correlation analysis and multivariate regression models were used to evaluate choroidal thickness or CVI with related factors.

RESULTS

The mean subfoveal CVIs were 0.35±0.10, 0.33±0.09, and 0.29±0.04, and the mean subfoveal choroidal thickness were 315.62±52.92, 306.22±59.29, and 262.69±45.55 µm in the F-APAC, F-CPACG, and normal groups, respectively. All macular sectors showed significantly higher CVIs and choroidal thickness in the F-APAC and F-CPACG eyes than in the normal eyes (P<0.05), while there were no significant differences between the F-APAC and F-CPACG eyes. In the peripapillary region, the mean overall CVIs were 0.21±0.08, 0.20±0.08, and 0.19±0.05, and the mean overall choroidal thickness were 180.45±54.18, 174.82±50.67, and 176.18±37.94 µm in the F-APAC, F-CPACG, and normal groups, respectively. There were no significant differences between any of the two groups in all peripapillary sectors. Younger age, shorter axial length, and the F-APAC or F-CPACG diagnosis were significantly associated with higher subfoveal CVI and thicker subfoveal choroidal thickness (P<0.05).

CONCLUSION

The fellow eyes of unilateral APAC or asymmetric CPACG have higher macular CVI and choroidal thickness than those of the normal controls. Neither CVI nor choroidal thickness can distinguish between eyes predisposed to APAC or CPACG. A thicker choroid with a higher vascular volume may play a role in the pathogenesis of primary angle-closure glaucoma.

Evaluation of retinal structure and function in prediabetes

Purpose

Alterations in retinal structure and function have been well documented in type 2 diabetes (T2DM). However, few studies have evaluated the eye in prediabetes (preDM), a precursor to T2DM. It is unknown which retinal deficits, if any, occur before T2DM diagnosis. This study evaluates retinal structure via optical coherence tomography (OCT) and retinal function via multifocal electroretinogram (mfERG) N1 and P1 in those with PreDM. The goal is to evaluate associations between structure and function across glucose dysfunction.

Methods

85 subjects (aged 28-69yrs) were tested with VERIS mfERG and Heidelberg Spectralis OCT. Demographic and health information was collected. Subjects were grouped by HbA1c: 33 controls (HbA1c <5.7%), 31 with preDM (HbA1c 5.7-6.4%), and 21 with T2DM (HbA1c >6.4% at the time of testing or diagnosed by physician) and mild or no retinopathy. mfERG N1 and P1 latency and amplitude were measured for the right eye in the foveal hexagon (central 2.4°). Average macular thickness was also measured over the central 3.3°. Groups were compared with ANOVA and corrected t-tests. Models of these associations with diabetes diagnosis (in groups above) were created with backward multivariate regression.

Results

The T2DM group was exceptionally well-controlled with an HbA1c of 7.0% ± 0.68 but also had elevated systolic blood pressure compared to other groups (P<0.01). The age of the control group was younger (P<0.01), so other testing was age controlled. There was a borderline but statistically significant difference in P1 between the control group and both the preDM and T2DM groups after Bonferroni corrections (P<0.03). There was also a difference in N1 latency between the control and other groups (P<0.001). A multivariate model demonstrated a significant relationship between T2DM/PreDM diagnosis and delayed N1 latency, reduced foveal thickness, and age.

Conclusions

Structure and function together can provide an associative model of preDM or T2DM changes for patients. Based on this multivariate model, N1 is strongly associated with preDM and T2DM. N1 findings and decreasing foveal thickness are additive and can together inform ocular health related to preDM. Future longitudinal studies are needed to understand changes in function and structure in preDM and T2DM.

Acute hyperglycemia compromises the responses of choroidal vessels using swept-source optical coherence tomography during dark and light adaptations

PURPOSE

To clarify the effects of acute hyperglycemia on the responses of choroidal structural components and vascularity index during light modulation in healthy participants using techniques including image binarization and artificial intelligence (AI) segmentation based on swept-source optical coherence tomography (SS-OCT).

METHODS

Twenty-four eyes of 24 healthy participants were imaged at different stages after ambient light, 40 min of dark adaptation, and 5 min of light adaptation in two imaging sessions: control and after receiving 75 g of oral glucose solution. The choroidal structural parameters, including luminal volume (LV), stromal volume (SV), total choroidal volume (TCV), and choroidal vascularity index (CVI) within a 6 mm area were determined using a custom algorithm based on image binarization and AI segmentation of SS-OCT. These measurements were compared among the conditions after adjusting for axial length, age to identify the differences.

RESULTS

In the dark, CVI decreased (-0.36 ± 0.09%) significantly in acute hyperglycemia compared to the control condition. During the transition to ambient light, there was an increasing trend in the choroidal parameters compared with the control experiment. However, only TCV (0.38 ± 0.17 mm³) and LV (0.27 ± 0.10 mm³) showed a significant increase at the time point of 5 min after ambient light.

CONCLUSION

Analysis of choroidal structural parameters and CVI based on SS-OCT images is a potentially powerful method to objectively reflect subtle changes in neurovascular coupling between the choroid and photoreceptor during dark adaptation.

Retinal Neurodegeneration in Euglycemic Hyperinsulinemia, Prediabetes, and Diabetes

Diabetic retinopathy (DR) is a challenging public health problem mainly because of its growing prevalence and risk of blindness. In general, our current knowledge and practice have failed to prevent the onset or progression of DR to sight-threatening complications. While there are treatment options for sight-threatening complications of DR, it is crucial to pay more attention to the early stages of DR to decrease its prevalence. Growing evidence suggests many pathologic changes occur before clinical presentations of DR in euglycemic hyperinsulinemia, prediabetes, and diabetes. These pathological changes occur in retinal neurons, glia, and microvasculature. A new focus on these preclinical pathologies - especially on hyperinsulinemia - may provide further insight into disease mechanisms, endpoints for clinical trials, and druggable targets in early disease. Here, we review the current evidence on the pathophysiological changes reported in preclinical DR and appraise preventive and treatment options for DR.

Optical coherence tomography evaluation of choroidal structure changes in diabetic retinopathy patients: A systematic review and meta-analysis

Introduction

Diabetic retinopathy (DR) is one of the major causes of blindness among working-aged adults worldwide. This study aimed to evaluate the differences in the subfoveal choroidal thickness (SFCT) and choroidal vascularity index (CVI) using optical coherence tomography (OCT) of patients with diabetic eyes with no retinopathy (NDR) and with diabetic retinopathy (DR).

Methods

We performed a comprehensive literature search of the PubMed, Embase, and Cochrane Library databases up to October 2021. The weighted mean difference (WMD) with the 95% confidence interval (CI) was pooled for continuous outcomes.

Results

Twenty-three cross-sectional studies comprising 2,534 eyes including 1,070 NDR eyes, 1,464 DR eyes were included in the systematic review and meta-analysis. The pooled results showed SFCT was significantly thicker in DR than in NDR patients after adjusting for axial length (WMD = 27.90 μm; 95% CI: 11.51 to 44.28; P = 0.001), and the CVI was significantly lower in DR patients (WMD = −1.59; 95% CI: −2.67 to −0.52; P = 0.004).

Conclusion

We described changes in the SFCT and CVI in DR. Resultantly, the CVI and SFCT may be valuable parameters for monitoring the onset of DR and helpful for a better understanding of the role of the choroid in the pathological process of DR.

Systematic review registration

https://www.crd.york.ac.uk/prospero/#myprospero, CRD42021228738.

Choroidal Assessment in Patients with Type 2 Diabetes Mellitus and Non-Proliferative Diabetic Retinopathy by Swept-Source Ocular Coherence Tomography and Image Binarization

Background and Objectives: The aim of this study was to evaluate choroidal structure and vascularity indices in patients with non-proliferative diabetic retinopathy (NPDR). Materials and Methods: Sixty-three eyes from sixty-three patients were evaluated: 21 from healthy subjects, 20 with diabetes mellitus (DM) and no diabetic retinopathy (DR), and 22 with DM and non-proliferative diabetic retinopathy without diabetic macular edema (DME). Each patient underwent ocular examination, macular swept-source ocular coherence tomography (SS-OCT) imaging, glycemic control, and systemic high blood pressure (HBP) evaluation. Subfoveal choroidal thickness (SF-CT) was manually assessed on a line scan. Line scan OCT images were exported to ImageJ program. The areas under a 1.5, 3 and 6 mm horizontal line centered on the fovea were assessed by converting the OCT images to binary images, and total choroidal area (TCA), luminal area (LA), stromal area (SA), LA:SA ratio, and choroidal vascularity index (CVI) were evaluated. SF-CT and choroidal parameters were compared between groups, and correlations with ocular and systemic factors were analyzed. Results: SF-CT, TCA, LA, and SA were similar between groups. CVIs were significantly different between groups for all three studied areas (CVI-1.5: 66.21% vs. 66.06% vs. 63.74%, p = 0.003; CVI-3: 65.88% vs. 66.46% vs. 63.79%, p = 0.008; CVI-6: 64.79% vs. 65.40% vs. 63.61%, p = 0.032). NPDR patients had significantly lower CVIs compared to DM patients (p < 0.05). No association of choroidal parameters with glycemic control, DM duration and HBP was found significant (p < 0.05). Conclusions: Choroidal assessment by SS-OCT and image binarization in healthy subjects, subjects with DM without DR, and subjects with DM and NPDR indicated that CVI changes were identifiable and significant in early DR. The lack of association with ocular and systemic factors suggest that CVIs are reliable assessment parameters of choroidal vascular structure.

Correlation between Choroidal Vascularity Index and Outer Retina in Patients with Diabetic Retinopathy

The choroid supplies blood to the outer retina. We quantified outer retinal and choroidal parameters to understand better the pathogenesis of diabetic retinopathy (DR) and diabetic macular edema (DME). The retrospective cross-sectional single-center study included 210 eyes from 139 diabetic patients and 76 eyes from 52 healthy controls. Spectral-domain optical coherence tomography (OCT) was carried out with a Spectralis HRA + OCT imaging device. The outer retinal layer (ORL), outer nuclear layer (ONL), and choroidal thicknesses were assessed along with the choroidal vascularity index (CVI). The presence of DR, whether with DME or without, was associated with choroidal thinning (p < 0.001). Compared with the controls, patients with DR without DME presented with lower ORL and ONL thickness (p < 0.001), whereas those with DR and DME had higher values of both parameters (p < 0.001). Significant correlations between outer retinal and choroidal parameters were found only in patients with DR without DME (ORL with choroidal thickness: p = 0.003, rho = 0.34; ORL with CVI: p < 0.001, rho = 0.49, ONL with CVI: p < 0.027, rho = 0.25). No correlations between choroidal and outer retinal parameters were observed in the controls and patients with DR and concomitant DME. Aside from diabetic choroidopathy, other pathogenic mechanisms seem to predominate in the latter group.